Cognitive radios (CR) utilize a variety of co-existence techniques in order to attempt to operate successfully along with existing wireless communication systems, architectures and other CR devices. The CR concept is generally intended to enable frequency band sharing and reuse with incumbent users and/or other CR devices. The manner by which CR performance can be increased or extended, via the use of advanced cognitive techniques, is of current interest in the communications arena.
The ability to share spectrum efficiently amongst existing CR devices presents challenges to designers of communication systems. Most spectral allocation techniques utilize a centralized control; however, a centralized control has the disadvantage of presenting a single point of failure. Even in a spectrum cleared of other users (i.e. cleared of incumbent users), achieving fair channel access among cooperating, yet independent, CR devices can be problematic. The ability for a new CR device to join a CR system and access the spectrum without having to undergo major changes to global infrastructure or coordinating access points of local area networks is not trivial.
Accordingly, it would be beneficial to have a CR device and CR system capable of efficient spectrum sharing.